1. Field of the Invention
The present invention relates generally to the preparation of rigid polyurethane foams, including those containing isocyanurate groups, of the type prepared using a condensation product of a polyethylene terephthalate with a low molecular weight polyol such as a glycol. In one aspect of the present invention, a thiodialkylene glycol is used as a raw material in the preparation of the polyethylene terephthalate condensation product to thus provide sulfur containing condensation products. In another aspect of the present invention, a rigid polyurethane foam is prepared from an organic polyisocyanate and the sulfur modified condensation product. In yet another aspect of the present invention, the thiodialkylene glycol is used as a cross linking agent in the preparation of rigid polyurethane foam from an aromatic polyisocyanate and the condensation product of a polyethylene terephthalate with a low molecular weight polyol such as a glycol.
2. Prior Art
Carlstrom et al. U.S. Pat. No. 4,223,068 discloses the manufacture of rigid polyurethane foam from a polyol of the type prepared by digesting a polyalkylene terephthalate with a low molecular weight polyol such as a diol or a triol to provide a condensation product. Among the low molecular weight polyols having a molecular weight of 500 or less disclosed by Carlstrom et al. are materials such as ethylene glycol, propylene glycol, butylene glycol, diethylene glycol, dipropylene glycol, etc.
Svoboda et al. U.S. Pat. No. 4,417,001 discloses the manufacture of polyurethane foams of the isocyanurate type using from 5 to 100% of a condensation product prepared by digesting a polyalkylene terephthalate with a low molecular weight polyol such as diethylene glycol.
Robinson U.S. Pat. No. 4,371,687 is directed to polytetramethylene ether glycols useful in the manufacture of polyurethanes. The polytetramethylene ether glycols are reacted with dihydroxyalkyl sulfides such as .beta.,.beta.'-dihydroxyethyl sulfide in the presence of an acid catalyst such as an alkyl or aryl sulfonic acid (which is preferably a strongly acidic cationic ion exchange resin containing --SO.sub.3 H groups) to provide a modified polytetramethylene ether glycol reaction product with the dihydroxydialkyl sulfide that has enhanced stability.
Copending U.S. patent application Ser. No. 553,272 filed Nov. 11, 1983, now U.S. Pat. No. 4,469,824 issued Sept. 4, 1984 for Grigsby et al. and entitled "Liquid Terephthalic Ester Polyols" discloses the manufacture of rigid polyurethane foam utilizing as a polyol component a condensation product prepared by digesting a polyethylene terephthalate with a mixture of oxyalkylene glycols, including diethylene glycol.
Robinson U.S. Pat. No. 4,373,084 is directed to polypropylene glycols useful in the manufacture of polyurethanes which are modified by having a thiodialkylene glycol incorporating therein.